<?php

/**
 * Encode in Base32 based on RFC 4648.
 * Requires 20% more space than base64  
 * Great for case-insensitive filesystems like Windows and URL's  (except for = char which can be excluded using the pad option for urls)
 *
 * @package default
 * @author Bryan Ruiz
 **/
class Base32Static {

   private static $map = array(
      'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', //  7
      'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', // 15
      'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', // 23
      'Y', 'Z', '2', '3', '4', '5', '6', '7', // 31
      '='  // padding character
    );
    
   private static $flippedMap = array(
      'A'=>'0', 'B'=>'1', 'C'=>'2', 'D'=>'3', 'E'=>'4', 'F'=>'5', 'G'=>'6', 'H'=>'7',
      'I'=>'8', 'J'=>'9', 'K'=>'10', 'L'=>'11', 'M'=>'12', 'N'=>'13', 'O'=>'14', 'P'=>'15',
      'Q'=>'16', 'R'=>'17', 'S'=>'18', 'T'=>'19', 'U'=>'20', 'V'=>'21', 'W'=>'22', 'X'=>'23',
      'Y'=>'24', 'Z'=>'25', '2'=>'26', '3'=>'27', '4'=>'28', '5'=>'29', '6'=>'30', '7'=>'31'
    );
    
    /**
     * Use padding false when encoding for urls
     *
     * @return base32 encoded string
     * @author Bryan Ruiz
     **/
    public static function encode($input, $padding = true) {
      if(empty($input)) return "";
      
      $input = str_split($input);
      $binaryString = "";
      
      for($i = 0; $i < count($input); $i++) {
        $binaryString .= str_pad(base_convert(ord($input[$i]), 10, 2), 8, '0', STR_PAD_LEFT);
      }
      
      $fiveBitBinaryArray = str_split($binaryString, 5);
      $base32 = "";
      $i=0;
      
      while($i < count($fiveBitBinaryArray)) {    
        $base32 .= self::$map[base_convert(str_pad($fiveBitBinaryArray[$i], 5,'0'), 2, 10)];
        $i++;
      }
      
      if($padding && ($x = strlen($binaryString) % 40) != 0) {
          if($x == 8) $base32 .= str_repeat(self::$map[32], 6);
          else if($x == 16) $base32 .= str_repeat(self::$map[32], 4);
          else if($x == 24) $base32 .= str_repeat(self::$map[32], 3);
          else if($x == 32) $base32 .= self::$map[32];
      }
      
      return $base32;
    }
    
    public static function decode($input) {
      if(empty($input)) return;
      
      $paddingCharCount = substr_count($input, self::$map[32]);
      $allowedValues = array(6,4,3,1,0);
      
      if(!in_array($paddingCharCount, $allowedValues)) return false;
      
      for($i=0; $i<4; $i++){ 
        if($paddingCharCount == $allowedValues[$i] && 
          substr($input, -($allowedValues[$i])) != str_repeat(self::$map[32], $allowedValues[$i])) return false;
      }
      
      $input = str_replace('=','', $input);
      $input = str_split($input);
      $binaryString = "";
      
      for($i=0; $i < count($input); $i = $i+8) {
        $x = "";
        
        if(!in_array($input[$i], self::$map)) return false;
        
        for($j=0; $j < 8; $j++) {
          $x .= str_pad(base_convert(@self::$flippedMap[@$input[$i + $j]], 10, 2), 5, '0', STR_PAD_LEFT);
        }
        
        $eightBits = str_split($x, 8);
        
        for($z = 0; $z < count($eightBits); $z++) {
          $binaryString .= ( ($y = chr(base_convert($eightBits[$z], 2, 10))) || ord($y) == 48 ) ? $y:"";
        }
      }
      
      return $binaryString;
    }
} 
